Organic Chemistry : Help with Alkene Reactions

Study concepts, example questions & explanations for Organic Chemistry

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Example Questions

Example Question #11 : Help With Alkene Reactions

The ozonolysis reaction involves the use of  (ozone gas) with alkene molecules. This reaction forms which of the following products?

Possible Answers:

Ethers

Carboxylic acids

Terpenes

Esters

Aldehydes

Correct answer:

Aldehydes

Explanation:

The ozonolysis of alkenes forms either ketones or aldehydes. Subsequent reagents can be added to produces alcohols and/or carboxylic acids. 

Example Question #11 : Help With Alkene Reactions

Screen shot 2015 12 20 at 10.37.19 pm

Which of the following is an intermediate in the hydration of ethylene for the reaction given?

Possible Answers:

Screen shot 2015 12 20 at 10.49.28 pm

Screen shot 2015 12 20 at 10.49.34 pm

Screen shot 2015 12 20 at 10.49.07 pm

Screen shot 2015 12 20 at 10.49.13 pm

Correct answer:

Screen shot 2015 12 20 at 10.49.07 pm

Explanation:

The reaction mechanism goes through a carbocation intermediate as follows:

 

Screen shot 2015 12 20 at 11.09.02 pm

 

Therefore the answer is the following carbocation intermediate:

Screen shot 2015 12 20 at 10.49.07 pm

Example Question #12 : Help With Alkene Reactions

Which of the followinng sets of addition reactions proceed via syn addition? 

Possible Answers:

Halohydrin addition, bromination

Bromination, catalytic hydrogenation

Halohydrin addition, epoxidation

Bromination, epoxidation

Hydroboration-oxidation, epoxidation

Correct answer:

Hydroboration-oxidation, epoxidation

Explanation:

Reactions that proceed by syn addition include hydrogenation, epoxidation, and hydroboration-oxidation. Reactions that proceed by anti addition include halogenation, halohydrin addition and epoxidation followed by ring opening. Syn addition occurs because reagents must approach from only one side of the double bond. 

Example Question #11 : Help With Alkene Reactions

Screen shot 2015 12 17 at 10.46.32 pm

Predict the product of the chemical reaction given.

Possible Answers:

Screen shot 2015 12 17 at 10.47.24 pm

Screen shot 2015 12 17 at 10.49.50 pm

Screen shot 2015 12 17 at 10.50.48 pm

Screen shot 2015 12 17 at 10.48.49 pm

Correct answer:

Screen shot 2015 12 17 at 10.47.24 pm

Explanation:

The reaction given is called a Markovnikov's addition reaction. This is a regiospecific reaction because only one orientation of the reaction occurs. It is an electrophilic addition reaction that involves the reaction of a halogenic acid such as  or  with an alkene. The hydrogen bonds to the carbon with the less alkyl groups bonded to the organic compound and the halogen ion bonds to the carbon with more alkyl substituents. Therefore the answer is:Screen shot 2015 12 17 at 10.47.24 pm

Example Question #15 : Help With Alkene Reactions

Screen shot 2015 12 17 at 11.23.40 pm

Predict the product of the chemical reaction given.

Possible Answers:

Screen shot 2015 12 17 at 11.23.48 pm

Screen shot 2015 12 17 at 11.23.53 pm

Screen shot 2015 12 17 at 11.24.07 pm

Screen shot 2015 12 17 at 11.24.02 pm

Correct answer:

Screen shot 2015 12 17 at 11.23.48 pm

Explanation:

The reaction given is called a Markovnikov's addition reaction. This is a regiospecific reaction because only one orientation of the reaction occurs. It is an electrophilic addition reaction that involves the reaction of a halogenic acid such as  or  with an alkene. The hydrogen bonds to the carbon with the less alkyl groups bonded to the organic compound and the halogen ion bonds to the carbon with more alkyl substituents. Therefore the answer is:Screen shot 2015 12 17 at 11.23.48 pm

Example Question #11 : Reactions By Reactant

Screen shot 2015 12 29 at 7.56.05 pm

Which of the following would be the product of the reaction given?

Possible Answers:

Screen shot 2015 12 29 at 7.56.42 pm

Screen shot 2015 12 29 at 7.56.31 pm

Screen shot 2015 12 29 at 7.56.26 pm

Screen shot 2015 12 29 at 7.56.49 pm

Correct answer:

Screen shot 2015 12 29 at 7.56.26 pm

Explanation:

Molecular chlorine reacts with an alkene in the presence of water to yield a halohydrin product. Below is the mechanism for this reaction:

Screen shot 2015 12 29 at 7.56.58 pm

Example Question #11 : Reactions By Reactant

Screen shot 2015 12 29 at 8.22.26 pm

Which of the following would be the product of the reaction given?

Possible Answers:

Screen shot 2015 12 29 at 8.23.30 pm

Screen shot 2015 12 29 at 8.23.25 pm

Screen shot 2015 12 29 at 8.23.34 pm

Screen shot 2015 12 29 at 8.26.49 pm

Correct answer:

Screen shot 2015 12 29 at 8.23.25 pm

Explanation:

Molecular bromine reacts with an alkene in the presence of water to yield a halohydrin product. Below is the mechanism for this reaction:

Screen shot 2015 12 29 at 8.23.16 pm

Example Question #11 : Help With Alkene Reactions

Screen shot 2016 01 10 at 9.31.00 pm

What is the major product of the reaction given?

Possible Answers:

Screen shot 2016 01 10 at 9.33.58 pm

Screen shot 2016 01 10 at 9.35.40 pm

Screen shot 2016 01 10 at 9.33.14 pm

Screen shot 2016 01 10 at 9.32.23 pm

Correct answer:

Screen shot 2016 01 10 at 9.33.58 pm

Explanation:

Alkenes react with NBS (N-bromosuccinimide) in the presence of light to giving products in the position next to the double called the allylic position. Below is the mechanism for this reaction:



Screen shot 2016 01 19 at 5.12.57 am

Example Question #21 : Reactions By Reactant

Screen shot 2016 01 10 at 9.24.24 pm

What is the major product of the reaction given?

Possible Answers:

Screen shot 2016 01 10 at 9.26.29 pm

Screen shot 2016 01 10 at 9.25.14 pm

Screen shot 2016 01 10 at 9.26.39 pm

Screen shot 2016 01 10 at 9.26.33 pm

Correct answer:

Screen shot 2016 01 10 at 9.25.14 pm

Explanation:

Alkenes react with NBS (N-bromosuccinimide) in the presence of light to giving products in the position next to the double called the allylic position. Below is the mechanism for this reaction:

Screen shot 2016 01 19 at 4.57.28 am

Example Question #21 : Reactions By Reactant

Screen shot 2016 01 24 at 4.38.11 pm

What is the product of the chemical reaction given?

Possible Answers:

Screen shot 2016 01 24 at 4.38.33 pm

Screen shot 2016 01 24 at 4.38.40 pm

Screen shot 2016 01 24 at 4.40.40 pm

Screen shot 2016 01 24 at 4.38.26 pm

Correct answer:

Screen shot 2016 01 24 at 4.38.26 pm

Explanation:

Hydroxylation of alkene compounds is called a hydration reaction. The reaction occurs in the presence of a strong acid catalyst to protonate the organic compound similar to Markovnikov's addition forming a carbocation as an intermediate. A water molecule nucleophilicly bonds to the carbocation intermediate. A proton is lost from the positively charged oxygen to a chloride ion yielding the alcohol product and regenerating the acid.

Screen shot 2016 01 24 at 4.38.17 pm

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